what is other ingredient with L- is it safe with other meds like maoi

OK first of all Leucine is added to the Benfotiamine because it is one of the three branched chain amino acids (BCAAs) that is unique in its ability to stimulate skeletal muscle protein synthesis. In fact, leucine has about a 10 fold greater impact on protein synthesis than any other amino acid! L-Leucine is like adding a turbo charger to you automobile to make it run more efficiently. Benfotiamine is a special type B vitamin that has been shown to prevent the accumulation of dangerous compounds that lead to diabetic neuropathy, the pain and cramps in the feet and legs that some diabetics have, and that's why I take it, and it works for me. After going to doctors for three years, and them telling me to just take aspirin for the pain and discomfort I decided to research my neuropathy myself, and through research in Germany I found they have been treating neurophathy successfully for decades with Benfotiamine with L-Leucine. This product can be taken on an empty stomach twice a day with any other medication because it has a different pathway in the body and will not interfere with other medications. I hope that helps you out my friend.

Has anyone with MS had any success with this vitamin treating their peripheral neuropathy?

I don't have MS but MG (Myasthenia Gravis) an auto-immune/muscular dystrophy (with peripheral neuropathy) and benfotiamine helps tremendously. On really bad flare-up days, it doesn't take away all the pain, but every little bit helps.

Why does it have Leucine in it?

According to the label:L-Leucine, 40mg per 300mg dose.

Is this sourced from or made in China

Not sure where the raw materials are sourced. However, if like most other supplements, OTC medicines and prescription drug raw materials they are likely sourced from China. It's estimated that 80-90% of raw materials for drugs, etc are sourced from China regardless of where they are ultimately manufactured. China has made it a priority to become the drug material supplier to the world and have been quite successful in accomplishing their goal. Sorry I cannot answer your question precisely. You would need to contact the manufacturer and then you can only hope that they even know where the ingredients are sourced. Most only know they obtain their materials from a 'supplier' in the USA.